Motor control system and method for selectively shorting motor windings

ABSTRACT

A motor control system shorts motor windings of a motor by using enhancement metal-oxide-semiconductor field-effect transistors (MOSFETs) so that the motor generates braking torque when all or some electric control units of the motor are disabled or failed. The motor control system comprises: a motor comprising a plurality of motor phase terminals; a plurality of electric control units electrically connected to the motor and configured to control the motor, wherein the electric control units configured to output control signals, respectively; a plurality of power sources, each of the power sources electrically connected to a respective one of the electric control units; and a shorting circuit connected between the power sources and the motor, the shorting circuit configured to selectively short the motor phase terminals in response to one or more of the control signals of the electric control units.

CROSS REFERENCE TO PARENT APPLICATION(S)

This application claims the benefit of U.S. Patent Application Ser. No.62/829,496, filed on Apr. 4, 2019, entitled “SSR Controlled BJT;Depletion FET Controlled BJT; Low Side MOSFET Turn ON with Resistor;Depletion Mode MOSFET; Enhancement Mode MOSFET”, which is all herebyincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure generally relates to an apparatus and method forcontrolling a motor. More specifically, some embodiments of the presentdisclosure relate to a motor control and method for selectively shortingmotor winding such that braking torque can be produced by the motor.

Vehicles require a steering system to control the direction of travel.Previously, mechanical steering systems have been used. Mechanicalsteering systems typically include a mechanical linkage or a mechanicalconnection between a steering wheel and vehicle's road wheels. Thus,movement of the steering wheel causes a corresponding movement of theroad wheels. Movement of such mechanical systems is often power assistedthrough the use of hydraulic assists or electric motors.

The mechanical steering systems are being replaced or supplemented byelectrically driven steering systems, commonly known as “steer-by-wire”systems. Such steer-by-wire systems to varying extents replace, forexample, the mechanical linkage between the steering wheel and thevehicle wheels with an electrically assisted actuator. The steer-by-wiresystem aims to eliminate physical or mechanical connection between asteering wheel and vehicle wheels by using electrically controlledmotors change the direction of the vehicle wheels and to providefeedback to a driver.

It is with respect to these and other general considerations that thefollowing embodiments have been described. Also, although relativelyspecific problems have been discussed, it should be understood that theembodiments should not be limited to solving the specific problemsidentified in the Background.

SUMMARY

The features and advantages of the present disclosure will be morereadily understood and apparent from the following detailed description,which should be read in conjunction with the accompanying drawings, andfrom the claims which are appended to the end of the detaileddescription.

Various embodiments of the present disclosure may provide a motorcontrol system configured to short motor windings of a motor so that themotor generates braking torque when all or some electric control unitsof the motor are disabled or failed.

According to some embodiments of the present disclosure, a motor controlsystem may comprise: a motor comprising a plurality of motor phaseterminals; a plurality of electric control units electrically connectedto the motor and configured to control the motor, wherein the electriccontrol units configured to output control signals, respectively; aplurality of power sources, each of the power sources electricallyconnected to a respective one of the electric control units; and ashorting circuit connected between the power sources and the motor, theshorting circuit configured to selectively short the motor phaseterminals in response to one or more of the control signals of theelectric control units.

The shorting circuit may be configured to, when receiving none of thecontrol signals from the electric control units, short the motor phaseterminals for braking of the motor. The shorting circuit may beconfigured, when receiving at least one of the control signals from atleast one of the electric control units, not to short the motor phaseterminals.

The shorting circuit may comprise: a plurality of first switches,wherein each of the first switches is connected between a respective oneof the power sources and a respective one of the motor phase terminals;and at least one second switch connected between the electric controlunits and the first switches, the at least one second switch isconfigured to cause the first switches to be turned on or off inresponse to at least one of the control signals from at least one of theelectric control units. The at least one second switch may be configuredto cause the first switches to be turned on to short the motor phaseterminals when receiving none of the control signals from the electriccontrol units. The at least one second switch may be configured to causethe first switches to be turned off not to short the motor phaseterminals when receiving at least one of the control signals from atleast one of the electric control units.

The first and second switches may be enhancementmetal-oxide-semiconductor field-effect transistors (MOSFETs). Forexample, the first and second switches are N-type enhancement MOSFETs.

The shorting circuit may comprise: a plurality of first MOSFETs, each ofthe first MOSFETs having first, second and third terminals, and at leastone second MOSFET having first, second and third terminals. The firstterminal of the at least one second MOSFET may be connected to theelectric control units to receive the control signals, the power sourcesmay be connected to the first terminals of the first MOSFETs and thesecond terminal of the at least one second MOSFET, and the secondterminal of each of the first MOSFETs may be connected to one respectiveof the motor phase terminals. The first terminals of the first andsecond MOSFETs may be gate, the second terminals of the first and secondMOSFETs may be drain, and the third terminals of the first and secondMOSFETs may be source. The third terminals of the first and secondMOSFETs are grounded. The third terminals of the first and secondMOSFETs may be connected to each other.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, in which:

FIG. 1 is a schematic view of a vehicle including a steer-by-wire systemaccording to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a motor control system according to anembodiment of the present disclosure; and

FIG. 3 is a conceptual circuit diagram of a circuit for selectivelyshorting motor phase terminals according to an embodiment of the presentdisclosure.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part of the present disclosure, andin which are shown by way of illustration specific embodiments in whichthe invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that structural, logical and electrical changes may be madewithout departing from the spirit and scope of the invention. Thefollowing detailed description is therefore not to be taken in alimiting sense, and the scope of the invention is defined only by theappended claims and equivalents thereof. Like numbers in the figuresrefer to like components, which should be apparent from the context ofuse.

Referring now to FIG. 1, a steer-by-wire system 10 for use in a vehicle1 is illustrated. The steer-by-wire system 10 allows a driver oroperator of the vehicle 1 to control the direction of the vehicle 1 orroad wheels 30 of the vehicle 1 through the manipulation of a steeringwheel 20. The steering wheel 20 is operatively coupled to a steeringshaft (or steering column) 22. The steering wheel 20 may be directly orindirectly connected with the steering shaft 22. For example, thesteering wheel 20 may be connected to the steering shaft 22 through agear, a shaft, a belt and/or any connection means. The steering shaft 22may be installed in a housing 24 such that the steering shaft 22 isrotatable within the housing 24.

The vehicle wheels 30 may be connected to knuckles, which are in turnconnected to tie rods. The tie rods are connected to a steering assembly32. The steering assembly 32 may include a steering actuator motor 34(e.g. an electric motor) and steering rods 36. The steering rods 36 maybe operatively coupled to the steering actuator motor 34 such that thesteering actuator motor 34 is adapted to move the steering rods 36. Themovement of the steering rods 36 controls the direction of the roadwheels 30 through the knuckles and tie rods.

One or more sensors 40 may configured to detect position, angulardisplacement or travel 25 of the steering shaft 22 or steering wheel 20,as well as detecting the torque of the angular displacement. The sensors40 provide electric signals to a controller 50 indicative of the angulardisplacement and torque 25. The controller 50 sends and/or receivessignals to/from the steering actuator motor 34 to actuate the steeringactuator motor 34 in response to the angular displacement 25 of thesteering wheel 20.

In use, the steering wheel 20 is angularly displaced 25 such that thesteering shaft 22 can be also angularly displaced. The sensors 40 detectthe angular displacement 25 of the steering shaft 22, and the sensors 40send signals to the controller 50 indicative of the relative amount ofangular displacement of the steering shaft 22. The controller 50 sendssignals to the steering actuator motor 34 indicative of the relativeamount of the angular displacement 30. In response, the steeringactuator motor 34 moves the steering rod 36 laterally so that the roadwheels 12 are turned. Thus, the controller 50 controls the distance thatthe steering rod 36 is moved based on the amount of the angulardisplacement 25 of the steering shaft 22. Movement of the steering rod36 manipulates the tie rods and knuckles to reposition the road wheels30 of vehicle 1. Accordingly, when the steering wheel 20 is turned, theroad wheels 30 are turned.

In the steer-by-wire steering system, the steering wheel 20 may bemechanically isolated from the road wheels 30. For example, thesteer-by-wire system has no mechanical link connecting the steeringwheel 25 from the road wheels 30. Accordingly, the steer-by wiresteering system needs to provide the driver or operator with the same“road feel” that the driver receives with a direct mechanical link.Furthermore, it is desirable to have a device that provides a mechanicalback up “road feel” in the event of multiple electronic failures in thesteer-by-wire system. In addition, a device that provides positiveon-center feel and accurate torque variation as the handwheel is rotatedis also desirable.

Therefore, the vehicle 10 may comprise a feedback actuator (FBA) orsteering feel actuator (SFA) 28. The feedback actuator or steering feelactuator 28 may comprise an electric motor (e.g. a motor 210 of FIG. 2)which is connected to the steering shaft or steering column 22. Forexample, a gear or belt assembly may connect an output of the feedbackactuator 28 to the steering shaft 22. Alternatively, the feedbackactuator 28 may be directly coupled to the steering shaft 22. Thefeedback actuator 28 is actuatable to provide resistance to rotation ofthe steering wheel 20. The controller 50 is operatively coupled to thesensors 40 and to the feedback actuator 28. The controller 50 receivessignals indicative of the applied torque and angular rotation of thesteering wheel 20 from the sensors 40. In response to the signals fromthe sensors 40, the controller 50 generates and transmits a signalcorresponding to the sensed torque and angular rotation of the steeringwheel 20 sensed by the sensors 40 and the feedback actuator 28 generatesresistance torque to the rotation of the steering wheel 20 in responseto the signal of the controller 50 to provide the road feel to thedriver. However, when the feedback of the feedback actuator 28 isremoved due to system failures such as inverter and it's controlfailures, the driver will have the uncomfortable feeling of beingseparated from the road wheels, not quite in control, and will tend tooversteer the vehicle, particularly in demanding situations such assharp or sudden turns.

Therefore, according to some embodiments of the present disclosure, amotor control system is configured to short motor windings of a motorincluded in the feedback actuator or steering feel actuator with batterypower available in a vehicle so that the motor provides the brakingtorque to the steering wheel when all or some electric control units ofthe feedback actuator or steering feel actuator are disabled or failed.This may prevent the driver oversteer.

FIG. 2 is a schematic diagram of a motor control system according to anembodiment of the present disclosure.

Power sources 200-1 to 200-N (N is a positive integer more than 1) areconfigured to supply power to a respective one of electric control units(ECUs) 1 to N. The power sources 200-1 to 200-N supply voltages to arespective one of ECUs 1 to N and a shorting circuit 220. For example,the power sources 200-1 to 200-N may be batteries 205-1 to 205-N. Thepower sources 200-1 to 200-N may be electrically connected to ECUs 1 toN through power lines PW-1 to PW-N and ground lines GND-1 to GND-N,respectively. The power sources 200-1 to 200-N may also be electricallyconnected to the shorting circuit 220 through the power lines PW-1 toPW-N and the ground lines GND-1 to GND-N. Therefore, the power sources200-1 to 200-N can supply power to the shorting circuit 220 even whenthe invertors INV 1-1 to INV N-M of the ECUs 1 to N are disabled orfailed.

The motor 210 may be, for example, but not limited to, a multi-phasemotor comprising a plurality of motor windings 215-1 to 215-M (M is apositive integer more than 1). The motor 210 may have a plurality ofmotor phase terminals MP-1 to MP-M connected to a respective one of themotor windings 215-1 to 215-M. For example, the motor 210 may be amulti-phase AC permanent magnet motor. In the present embodiment, themotor 210 may be a three-phase permanent magnet motor having a U-phasewinding 215-1, a V-phase winding 215-2, and a W-phase winding 215-3.

The ECUs 1 to N comprise multi-phases (M-phases) inverters INV 1-1 toN-M. inverters INV 1-1 to N-M are coupled to the motor phase terminalsMP-1 to MP-M connected to a respective one of the motor windings 215-1to 215-M. The inverters INV 1-1 to N-M receive power from the powersources 200-1 to 200-N, and convert direct current (DC) voltagesprovided from the power sources 200-1 to 200-N to alternating currents(AC). The outputs generated by the inverters INV 1-1 to N-M are appliedto the motor windings the motor windings 215-1 to 215-M through themotor phase terminals MP-1 to MP-M to drive the multi-phase (M-phase)motor 210. The ECUs 1 to N also generate control signals CTL 1 to N. Thecontrol signals CTL 1 to N may have substantially the same voltage asbattery voltages of the batteries 205-1 to 205-N of the power sources200-1 to 200-N.

The ECUs 1 to N may have, for example, but not limited to, one or moreof a circuit, microprocessor or computer, which monitors and physicallyalters the operating conditions of the motor control system 15. Thecontroller ECUs 1 to N may also be configured to accept input and outputfrom a wide array of input and output devices for receiving or sendingvalues.

The shorting circuit 220 is connected between the power sources 200-1 to200-N and the motor 210. The shorting circuit 200 is configured toselectively short the motor phase terminals MP-1 to MP-M in response toone or more of the control signals CTL-1 to CTL-N received from the ECUs1 to N. For example, when the shorting circuit 220 receives no controlsignal from all of the ECUs 1 to N, such as in the case that all ECUs 1to N are disabled or failed (for example, all invertors of ECUs 1 to Nare disabled or failed), the shorting circuit 220 is configured to shortthe motor phase terminals MP-1 to MP-M so that the motor 210 cangenerate the braking torque. However, when the short circuit 220receives at least one of the control signals CTL-1 to CTL-N from atleast one of the ECUs 1 to N, such as in the case that any one of theECUs 1 to N is enabled, the shorting circuit 220 configured to removethe short of the motor phase terminals MP-1 to MP-M or does not shortthe motor phase terminals MP-1 to MP-M.

FIG. 3 is a conceptual circuit diagram of the shorting circuit 220according to an embodiment of the present disclosure.

The shorting circuit 220 may comprise a plurality of first switches S1-1to S1-M. The first switches S1-1 to S1-M are connected to the motorphase terminals MP-1, MP-2, MP-3, respectively. The first switches S1-1to S1-M may short the motor phase terminals MP-1 to MP-M when the firstswitches S1-1 to S1-M are turned on. However, when the first switchesS1-1 to S1-M are turned off, the switches S1-1 to S1-M may not short themotor phase terminals MP-1 to MP-M or may remove the short of the motorphase terminals MP-1 to MP-M. The number of the first switches S1-1 toS1-M may correspond to the number of the phases of the motor 210. Forinstance, in the embodiment of FIG. 3, because the motor 210 is athree-phase motor, the shorting circuit 220 has three (3) first switchesS1-1, S1-2, S1-3. However, the shorting circuit 220 may have thedifferent number of the first switches S1-1 to S1-M from the number ofthe phases of the motor 210

For illustration purposes, in this exemplary embodiment shown in FIG. 3,the motor 210 is a three-phase motor having phases U, V, W and two (2)ECUs. ECU 1 and ECU 2, and two (2) power sources 200-1 and 200-2 areconnected to the shorting circuit 220. However, the present disclosureis not limited thereto.

The first switches S1-1, S1-2, S1-3 may be enhancementmetal-oxide-semiconductor field-effect transistors (MOSFETs). In theembodiment of FIG. 3, the first switches S1-1, S1-2, S1-3 areillustrated as N-type MOSFETs for illustration purposes only. However,one skilled in the art will recognize that other transistor typesincluding P-type MOSFETs could be used instead of the N-type MOSFETsshown in this illustrative example, the substitution could be made toreplace the N-type MOSFETs with P-type MOSFETs. Further, any switch,such as a transistor, which is turned off when a voltage between a firstterminal of the switch and a second terminal of the switch is below athreshold and is turned off when the voltage between the first terminalof the switch and the second terminal of the switch is above thethreshold, can be used instead of the MOSFETs.

The shorting circuit 220 receives input voltages from the power sources200-1 and 200-2 of FIG. 2 through terminals PT-1 and PT-2, respectively.The input voltages received from the power sources 200-1 and 200-2 areprovided to first terminals (e.g. gates) of the first MOSFETs S1-1,S1-2, S1-3. Optionally, Diodes D1-1 and D1-2 may be coupled in series tothe terminals PT-1 and PT-2, respectively, to prevent backward path tothe power sources 200-1 and 200-2. A diode D2 may be coupled in parallelto the first terminals (e.g. gates) of the first MOSFETs S1-1, S1-2,S1-3 to protect gate voltages, and a pull down resistor R1 may becoupled between the first terminals (e.g. gates) and second terminals(e.g. sources) of the first MOSFETs S1-1, S1-2, S1-3.

A third terminal (e.g. drain) of the first MOSFET S1-1 is connected to aU-phase motor terminal MP-1 connected to the motor winding 215-1, athird terminal (e.g. drain) of the first MOSFET S1-2 is connected to aV-phase motor terminal MP-2 connected to the motor winding 215-2, and athird terminal (e.g. drain) of first MOSFET S1-3 is connected to aW-phase motor terminal MP-3 connected to the motor winding 215-3.

The shorting circuit 220 further includes one or more second switchesS2. The second switch S2 can be, for example, but not limited to, anenhancement MOSFET. In the embodiment of FIG. 3, the second switch S2 isillustrated as N-type MOSFET for illustration purposes only. However,one skilled in the art will recognize that other transistor typesincluding P-type MOSFET could be used instead of the N-type MOSFET shownin this illustrative example, the substitution could be made to replacethe N-type MOSFET with P-type MOSFET. Further, any switch, such astransistor, which is turned off when a voltage between a first terminalof the switch and a second terminal of the switch is below a thresholdand is turned off when the voltage between the first terminal of theswitch and the second terminal of the switch is above the threshold, canbe used instead of the MOSFET.

The second MOSFET S2 causes the first MOSFETs S1-1, S1-2, S1-3 to beturned on or off in response to one or more of control signals CTL 1 andCTL 2 received from ECUs 1 and 2. For example, if the second MOSFET S2receives no control signal from all of ECUs 1 and 2, the first MOSFETsS1-1, S1-2, S1-3 are turned on so that the motor phase terminals MP-1 toMP-M are shorted. However, if the second MOSFET S2 receives a controlsignal from any one of ECUs 1 and 2, the first MOSFETs S1-1, S1-2, S1-3are turned off and the motor phase terminals MP-1 to MP-M are notshorted by the first MOSFETs S1-1, S1-2, S1-3.

For instance, a first terminal (e.g. gate) of the second MOSFET S2 isconnected to the ECUs 1 and 2 through terminals C-1 and C-2 to receivecontrol signals CTL 1 and CTL 2 from the ECUs 1 and 2. Optionally, adiode D3 may be coupled in parallel to the first terminal (e.g. gate) ofthe second MOSFET S2 to protect a gate voltage, and a pull down resistorR2 may be coupled between the first terminal (e.g. gate) and the secondterminal (e.g. source) of the second MOSFET S2. The second terminal(e.g. source) of the second MOSFET S2 may be grounded. For example, thesource of the second MOSFET S2 is connected to the grounds of the powersources 200-1 and 200-2 through ground terminals GT-1 and GT-2.

In operation, when all of the ECUs 1 and 2 are disabled or failed (forinstance all of invertors of the ECUs 1 and 2 are disabled or failed),voltages of control signals CTL 1 and CTL 2 inputted from the ECUs 1 and2 through the terminals CT-1 and CT-2 are at 0V. Then, because thegate-source voltage of the second MOSFET S2 is 0V, the second MOSFET S2is turned off. This makes the gate-source voltages of the first MOSFETsS1-1, S1-2, S1-3 at approximately battery voltages of the batteries205-1 and 205-2 of the power sources 200-1 and 200-2 since the terminalsPT1 and PT2 provide the battery voltages of batteries 205-1 and 205-2 ofthe power sources 200-1 and 200-2 to the gates of the first MOSFETsS1-1, S1-2, S1-3. In turn, the first MOSFETs S1-1, S1-2, S1-3 are turnedon and short the motor phase terminals MP-1, MP-2, MP-3. This results inthe braking of the motor 210. The motor 210 may act as a brake and/ordamper to oppose any motion applied to the motor 210.

However, if any one of the ECUs 1 and 2 is enabled, voltages of controlsignals CTL1 and CTL2 inputted from the ECUs 1 and 2 through CT-1 andCT-2 are at approximately the battery voltage. Then, because thegate-source voltage of the second MOSFET S2 is at approximately thebattery voltage, the second MOSFET S2 is turned on. This makes thegate-source voltages of the first MOSFETs S1-1, S1-2, S1-3 belowthreshold voltages of the first MOSFETs S1-1, S1-2, S1-3. In turn, thefirst MOSFETs M1-1, M1-2, M1-3 are turned off and does not short themotor phase terminals MP-1, MP-2, MP-3 or remove the motor 210 from theshort status.

Therefore, when all invertors INV 1-1 to INV N-M of the ECUs 1 to N aredisabled or failed, the shorting circuit 220 is configured to short themotor phase terminals MP-1 to MP-M connected to the motor windings 215-1to 215-M so that the motor 210 can generate the braking torque. In thecase that the motor 210 is included in the feedback actuator or steeringfeel actuator 28, the feedback actuator or steering feel actuator 28 maygenerate the braking torque to the steering wheel 20 and prevent fromproviding uncomfortable feeling of being separated from the road wheelsto the driver or oversteering the vehicle by the driver when all or someelectric control units of the feedback actuator or steering feelactuator 28 are disabled or failed.

In some embodiments of the present disclosure, the motor for thefeedback actuator or steering feel actuator is described, but thepresent disclosure is not limited thereto. However, one skilled in theart will recognize that the motor control system according to thepresent disclosure could be applied to or used with any motor thatrequires braking and/or damping torque.

Although the example embodiments have been described in detail, itshould be understood that various changes, substitutions and alterationscan be made herein without departing from the spirit and scope of theapplication as defined by the appended claims.

In the present disclosure, relational terms such as first and second,and the like may be used solely to distinguish one entity or action fromanother entity or action without necessarily requiring or implying anyactual such relationship or order between such entities or actions.Furthermore, depending on the context, words such as “connect” or“coupled to” used in describing a relationship between differentelements do not imply that a direct physical connection must be madebetween these elements. For example, two elements may be connected toeach other physically, electronically, logically, or in any othermanner, through one or more additional elements. The term “connected” or“coupled” may mean direct or indirect connection unless otherwisespecified.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, and composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure, processes, machines,manufacture, compositions of matter, means, methods or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to theembodiments and alternative embodiments. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1-13. (canceled)
 14. A steering apparatus, comprising: a steering shaftoperatively coupled to a steering wheel of a vehicle; a motoroperatively coupled to the steering shaft, and comprising a plurality ofmotor phase terminals; a shorting circuit disposed between the motor anda power source of the vehicle; and a processor electrically coupled tothe motor and the shorting circuit, and configured to control the motor,wherein the processor is configured to control the shorting circuit toselectively short at least two terminals of the motor phase terminals.15. The steering apparatus of claim 14, wherein the processor isconfigured to control the shorting circuit to short the motor phaseterminals for braking of the motor when receiving none of a controlsignal from the processor.
 16. The steering apparatus of claim 14,wherein the processor is configured to control the shorting circuit notto short the motor phase terminals when receiving a control signal fromat least one of the processor.
 17. The steering apparatus of claim 14,wherein the shorting circuit comprises: a plurality of first switches,wherein each of the first switches is connected between the power sourceand a respective one of the motor phase terminals; and at least onesecond switch connected between the processor and the first switches,the at least one second switch is configured to cause the first switchesto be turned on or off in response to a control signal from theprocessor.
 18. The steering apparatus of claim 17, wherein the at leastone second switch is configured to cause the first switches to be turnedon to short the motor phase terminals when receiving none of the controlsignal from the processor.
 19. The steering apparatus of claim 17,wherein the at least one second switch is configured to cause the firstswitches to be turned off not to short the motor phase terminals whenreceiving the control signal from the processor.
 20. The steeringapparatus of claim 17, wherein the first and second switches areenhancement metal-oxide-semiconductor field-effect transistors(MOSFETs).
 21. The steering apparatus of claim 17, wherein the first andsecond switches are N-type enhancement MOSFETs.
 22. The steeringapparatus of claim 14, wherein: the shorting circuit comprises: aplurality of first MOSFETs, each of the first MOSFETs having first,second and third terminals, and at least one second MOSFET having first,second and third terminals; and the first terminal of the at least onesecond MOSFET is connected to the processor to receive the controlsignal, the power source is connected to the first terminals of thefirst MOSFETs and the second terminal of the at least one second MOSFET,and the second terminal of each of the first MOSFETs is connected to onerespective of the motor phase terminals.
 23. The steering apparatus ofclaim 22, wherein the first and second MOSFETs are enhancement MOSFETs.24. The steering apparatus of claim 22, wherein first and second MOSFETsare N-channel enhancement MOSFETs.
 25. The steering apparatus of claim22, wherein the first terminals of the first and second MOSFETs aregate, the second terminals of the first and second MOSFETs are drain,and the third terminals of the first and second MOSFETs are source. 26.The steering apparatus of claim 22, wherein the third terminals of thefirst and second MOSFETs are connected to each other.